XII.] UNEXHAUSTED MANURES-COMPENSATION 355 



question. To a certain extent, again, the value of the 

 residue left by a particular fertiliser will be determined 

 by the nature of the land and the crop to which it has 

 been applied ; kainit applied to heavy clay land would 

 not add to the value of the land, but on the other hand 

 the benefit derived from the application of fertilisers to 

 grazing land is largely cumulative, depending upon the 

 change it effects in the botanical composition and 

 quality of the herbage, so that the benefit may be 

 greater at the end of the third or fourth year after 

 application than earlier. Certainly no a priori rules for 

 compensation based upon purely theoretical considera- 

 tions can be laid down ; any scale of compensation must be 

 based upon experiments only and must always be con- 

 sidered as approximate and subject to revision according 

 to the particular conditions of soil and cropping. 



Experiments instituted at Rothamsted to provide 

 data for drawing up such a scale have not progressed 

 far enough to eliminate the experimental error that 

 occurs in dealing with such small quantities as are 

 involved in the residual effects of most fertilisers after 

 one or two crops have been grown. The crude practice 

 adopted by many valuers of allowing to the outgoing 

 tenant half the cost of the purchased fertilisers he has 

 applied during the last year of his tenancy, can find 

 little or no justification, and in the case of such sub- 

 stances as nitrate of soda and sulphate of ammonia is 

 obviously unjust to the incoming tenant, unless the 

 manure has been applied to root crops which have been 

 consumed on the farm. The whole subject is very 

 complex, and data do not as yet exist for constructing 

 any table that would serve as a basis for valuation, for 

 the compensation to be awarded will always have to be 

 decided on the merits of each case after due considera- 

 tion of the soil and other local circumstances. 



